In a sense your question is the $64,000 question. No one knows for sure what camo scheme USS FLETCHER had when she arrived in the Pacific. It is known from photos that USS FLETCHER was delivered and went on Shakedown painted in Ms 12R(mod). But, with the new camo directives starting to be applied to ships in roughly August 1942, things started to change. The Pacific Fleet had already directed that all their ships were to be painted in Ms 11 with 5-N, which became Ms 21 in the new schemes. The Atlantic Fleet decided to go with Ms 22 graded scheme.
It is known that of the first three FLETCHER's to arrive in the Pacific, the first two from photos, USS NICHOLAS and USS O'BANNON were painted by BosNY in what is called Ms 18. It isn't clear if this was an official scheme, it isn't listed in the "official list" of new camo schemes authorized in the summer of 1942. But, it was used enough to be noted as more than just a "one-off" experiment and lasted into 1944. Also, it can't be a "miss-applied" Ms 22 because ships were painted with Ms 18 in the same yard as others were painted with Ms 22. I have counted over three dozen destroyers (plus a few cruisers) that had this scheme applied. Ms 18 was more or less a throwback to original Ms 12 with only two colors used. The hull from the main deck "SHEER" line (not parallel to the waterline as in Ms 22) down was painted with 5-N. Everything above that line was painted with 5-H. On FLETCHER's Ms 18 means that the whole hull was painted in 5-N and the superstructure was painted with 5-H.
I have noted that in August 1942, just about every destroyer that was fitting out or in a major yard period at Boston Navy Yard was painted in Ms 18. However, USS FLETCHER was home-ported at NYNY and after shakedown in July-August 1942, she went into the NYNY for post-shakedown work prior to heading to the Pacific, with USS O'BANNON and after USS NICHOLAS. The August yard period is when FLETCHER had the fantail twin 40-mm mount installed. This would have been an ideal and quite likely time for her to be repainted or at least be "touched-up". The question is, since no photos have surfaced from late August 1942 until early in 1943, was FLETCHER repainted in something other than Ms 12R(Mod)? The Pacific Fleet was requiring that Ms 21 be applied and it could have been done at NYNY or was the Ms 18 scheme used?
In the Pacific, PacFlt noting that many of the ships transferring from the Atlantic Fleet, were in non-Ms 21 schemes, directed in mid-October 1942, that ALL ships not painted in Ms 21 were to repaint to it as "soon as operationally possible". I have documentation that USS O'BANNON did repaint to Ms 21 in early November 1942.
USS NICHOLAS arrived in the forward South Pacific area on 14 September 1942, USS O'BANNON (departed BosNY on 29 August) and USS FLETCHER (departed NYNY on 4 September) arrived on 5 October 1942.
All the FLETCHER's that arrived after these three arrived painted in something other than Ms 12R(Mod). Many were painted in Ms 22 because they first operated in the Atlantic during Shakedown and were not repainted until AFTER they arrived in the South Pacific forward area.
Bottomline, you can choose which scheme you "think" it should be. Ms 12R(Mod), Ms 18, or Ms 21 as she was known to have been painted to by at least January 1943.
As for images of USS FLETCHER while she was painted in Ms 12R(Mod) and BEFORE her fantail 40-mm mount was installed, these two images (as delivered in June 1942 and as she departed for Shakedown in July 1942) show her port and starboard sides. Colors are 5-N, 5-O, and 5-H;
Here is an onboard view of USS FLETCHER with the photo dated 5 January 1943. Whether this is the ACTUAL date is uncertain (quite likely dates earlier), but is the earliest view of her in the Pacific I have come across. It is open to interpretation as to what her paint scheme is, but to me it doesn't look like Ms 12R(Mod).
As an example of what Ms 18 looked like on a FLETCHER, here is a view of USS O'BANNON on 12 October 1942 as she escorted USS COPAHEE (CVE-12).

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If you are going to say Measure 12 modified, how was it applied to hull and superstructure and in what colors.
Thank you for any help.